Figure 7.

Functional relationship between Ste9 and Rum1. (A) Changes of Rum1 protein level after starvation. The ste9-B36 Δcig2 rum1⁺-3HA strain (KJ238–7B) was transformed with a vector or the ste9⁺-plasmid. Both strains cultured in EMM2 were shifted to nitrogen-free medium. At the indicated time, samples were taken for immunoblotting. (B) DNA content of ste9⁺ or ste9⁻ cells in the absence of cig2 function. Samples from the same cultures described in panel A were analyzed by flow cytometry. (C) Mutual suppression of synthetic lethality by either rum1⁺- or ste9⁺-plasmid. Cells of Δste9 wee1–50 Δcig2 (KJ111–1A, upper panel) or Δrum1 wee1–50 (KJ152–9A, lower panel) were transformed with the vector, pAL(ste9), and pREP1(rum1). Each transformant was streaked onto EMM2 plates containing 5 μM thiamine and incubated for 3 d at 34.5°C. (D) Suppression of the synthetic lethality at semipermissive temperature for cdc10 cells. Cells of Δste9 cdc10-V50 (KJ218–2B) were transformed with the vector, pAL(ste9), and pAL(rum1). Transformants were incubated at 30°C for 3 d (upper panel). Cells of Δrum1 cdc10–129 (Sp224) were transformed with the same plasmids, and then incubated at 32°C for 3 d (lower panel).